1. Field of the Invention
The present invention relates to a vacuum-treatment apparatus, in particular, to a vacuum-treatment apparatus used in a semiconductor production process, such as dry etching, CVD, deposition, sputter deposition and the like in which a specimen is treated while pressing it against a specimen table.
2. Description of the Related Art
FIG. 2 is a schematic sectional view showing a dry etching apparatus, a conventional vacuum-treatment apparatus. In FIG. 2, a reaction chamber 1 of the dry etching apparatus is an airtight container which is provided with a gas-feeding entrance 2 and an exhaust port 3. An upper electrode 4 and specimen table 5, acting as a lower electrode, are provided at upper and lower portions of the reaction chamber 1. These electrodes are electrically connected and an RF generator 6 and a coupling capacitor 7 are connected in series with the electrodes. A specimen 8, i.e., a semiconductor wafer, is disposed on the surface of the specimen table 5, the outside of which is surrounded with a clamp ring 9 and clamp pins 10 which make the clamp ring move up and down. A clamp driving unit 11 which operates the clamp pins 10 is positioned exterior to the specimen table 5. A detailed description of the mechanism of the clamp driving unit 11 is omitted.
The conventional dry etching apparatus is constructed as described above. At first the specimen 8 is placed onto the specimen table 5 while the clamp ring 9 is in a raised position. The clamp pins 10 are moved down by the clamp driving unit 11. The clamp ring 9, which is mounted on the clamp pins 10, contact the outer circumference of the specimen 8. The specimen 8 is secured to the specimen table 5 by the desired pressure which is controlled by the power of the clamp driving unit 11. A reactive gas is fed into the reaction chamber 1 through the gas-feeding entrance 2 and an adequate quantity of the gas is exhausted from the exhaust port 3 so that the inside of the reaction chamber 1 is maintained at a predetermined pressure.
An RF voltage is applied by the RF generator 6 between the specimen table 5, acting as a lower electrode, and the upper electrode 4. Matching of impedance is performed by the coupling capacitor 7 so that a plasma of the reactive gas is generated in the reaction chamber 1 and the surface of the specimen 8 is etched. Then, the back of the specimen 8 is firmly pressed to the surface of the specimen table 5 by the pressure of the clamp ring 9. The heat transfer efficiency between the specimen 8 and the specimen table 5 is high and heat from the specimen 8, raised by the plasma, is absorbed into the specimen table 5. If an operator is required to set the temperature of the specimen 8 higher or lower than room temperature, he sets the temperature of the specimen table 5 at a desired temperature beforehand. The temperature of the specimen 8 can be changed to a desired value in a short time because of thermal transfer efficiency.
In the dry etching apparatus, the surface of a specimen, such as a silicon wafer, is etched by the plasma of the reactive gas which is generated in the reaction chamber 1 and the temperature of the specimen 8 rises during the process because of heat transfer from the plasma. The dry etching apparatus has a fundamental problem in that various characteristics such as the etching rate, uniformity of the etching rate on the surface of the semiconductor wafer and various etching rates according to the difference of materials etched, change with a rise in the temperature of the specimen 8. Superior characteristics are manifested when the specimen 8 is set at an optimum temperature higher or lower than room temperature. As described above, temperature control of the specimen 8 is a very serious problem and an attempt is made to control the temperature of the specimen 8 by controlling the contact between the specimen 8 and the specimen table 5.
In the above-described vacuum-treatment apparatus, in order to control the temperature of the specimen 8, i.e. to make the specimen 8 the same temperature as the specimen table 5, the specimen 8 is pressed against the specimen table 5 by using a mechanism in which the clamp pins 10 are moved up and down by the driving unit. Therefore, the construction of members such as clamp pins 10 and holes, through which the clamp pins 10 pass, is complicated and because there are many surfaces mechanically in contact one another, the amount of dust-generation is increased. This is a problem of semiconductor manufacturing apparatus. Such dust-generation must be sufficiently controlled in future semiconductor manufacturing apparatus which will require more precision.